The present invention relates to directional horizontal boring and more specifically to a backreamer design generally referred to as a winged cutter with fluid jets positioned outward on said cutter wings.
Backreamers in directional drilling have been available since the earliest developments of directional technology. A backreamer is a downhole tool that increases the diameter of a pilot bore hole. Usually on the pull-back phase of a directional drilling bore, the permanent casing or the utility lines are pulled behind the reamer through a swivel back through the enlarged bore hole. There are many different types of reamers utilized with various soil conditions, such as cones with teeth, spiral cutters, fluted cone backreamers, and winged backreamers.
Winged backreamers apply tremendous bending loads on the base of the wings due to their long moment arms, thereby applying substantial loads at the juncture point of the wings with the axle. A prior art method of dealing with these loads is to connect the outer ends of the reamer wings by a ring structure which transmits the bending loads on one wing to the remaining wings on the backreamer, thereby transferring or spreading the load. Backreamers with rings create additional drag and potential blockage problem which a cantilevered wing would not have. The load on the wings can also be diminished by lengthening the base portion of the wing where it is welded to the axle to increase the cross-sectional area of the welded joint between the wing and the axle of the backreamer.